The incubator having the above arrangement has been conventionally known as disclosed in Japanese Patent Laid-Open No. 09-206345. In the incubator (to be referred to as “the incubator in the above patent reference” hereinafter) disclosed in Japanese Patent Laid-Open No. 09-206345, a tray loading/unloading port is provided on the front side of a cassette tray accommodation space formed between an incubator base and a bed base.    Patent Reference: Japanese Patent Laid-Open No. 09-206345
With the incubator in the above patent reference, however, the tray loading/unloading port is provided only on the front side of the cassette tray accommodation space. Therefore, when a doctor or nurse performs an operation such as medical treatment in a region including the front side of the cassette tray accommodation space and its vicinity, it is impossible to store or take out a cassette tray in or from the cassette tray accommodation space unless he/she leaves the region including the front side of the cassette tray accommodation space and its vicinity. In addition, if a sophisticated article such as a sophisticated medical apparatus exists in a region, outside the cassette tray accommodation space, including the front side of the cassette tray accommodation space and its vicinity, it is necessary to move the sophisticated article to another position or change the position or orientation of the incubator.
The present invention effectively solves the above problem in the incubator in the above patent reference with a relatively simple arrangement.